🔌 E1 Multiplexer & Demultiplexer Virtual Laboratory

Interactive Simulation for Data Communication Undergraduate Students

1. Introduction to E1 System

The E1 is a digital transmission link that carries 30 simultaneous telephone calls (or data channels) plus 2 signaling channels, totaling 32 time slots. It is the European equivalent of the T1 line used in North America and operates at a rate of 2.048 Mbps.

Key Characteristics:
  • Total Data Rate: 2.048 Mbps
  • Number of Channels: 30 voice/data + 2 signaling = 32 time slots
  • Frame Structure: 32 time slots × 8 bits = 256 bits per frame
  • Frame Duration: 125 μs (8000 frames per second)
  • Line Code: HDB3 (High Density Bipolar 3 zeros)

2. E1 Frame Structure

An E1 frame consists of 32 time slots (TS0 to TS31), each carrying 8 bits. The frame is transmitted every 125 microseconds.

Frame Rate = 8000 frames/second
Bit Rate = 32 slots × 8 bits × 8000 = 2,048,000 bps = 2.048 Mbps

Time Slot Allocation:

  • TS0: Frame alignment word (synchronization) - alternates between fixed patterns
  • TS1-TS15: Voice/data channels 1-15
  • TS16: Signaling channel (CAS - Channel Associated Signaling)
  • TS17-TS31: Voice/data channels 16-30

E1 Frame Structure (32 Time Slots)

Sync (TS0)
Signaling (TS16)
Data Channels (TS1-15, TS17-31)

3. Multiplexing Process

Time Division Multiplexing (TDM) is the technique used in E1 systems. Multiple lower-rate signals are combined into a single higher-rate signal by allocating specific time slots to each input channel.

E1 Multiplexer Operation:

  1. Input Buffering: 30 input channels (64 kbps each) are buffered
  2. Sampling: Each channel sampled at 8 kHz (every 125 μs)
  3. Encoding: Each sample encoded into 8 bits (A-law or μ-law PCM)
  4. Frame Assembly: Bits from all channels assembled into 256-bit frame
  5. Insertion: TS0 (sync) and TS16 (signaling) inserted
  6. Line Coding: HDB3 encoding for transmission
Multiplexer Output = Σ (Channel i data) + Overhead bits
where i = 1 to 30 channels

4. Demultiplexing Process

The demultiplexer performs the reverse operation, extracting individual channels from the composite E1 stream.

E1 Demultiplexer Operation:

  1. Clock Recovery: Extract timing from received signal
  2. Frame Synchronization: Detect TS0 alignment word
  3. Decoding: HDB3 decoding to recover binary data
  4. Time Slot Extraction: Route each TS to appropriate output
  5. Signaling Extraction: Process TS16 for call control
  6. Output Buffering: Smooth data for individual channels

5. Signaling in E1 (TS16)

Channel Associated Signaling (CAS) uses TS16 to carry supervisory states (on-hook/off-hook) for each voice channel.

Multiframe Structure:
  • 16 consecutive frames form a multiframe (2 ms duration)
  • TS16 in Frame 0: Multiframe alignment word
  • TS16 in Frames 1-15: Signaling for channels (2 channels per frame)
  • Each channel gets 4 signaling bits (A, B, C, D)

🎛️ Interactive E1 Multiplexer/Demultiplexer Simulation

0
Frames Processed
2.048
Mbps
8
Active Channels
🔒 Locked
Sync Status

Input Channels (Demultiplexer Input / Multiplexer Output)

Multiplexer: Time Domain Waveform
Demultiplexer: Channel Separation

Live Frame Assembly Animation

🧪 Laboratory Procedure

1Pre-Lab Preparation

  • Review the theory of Time Division Multiplexing (TDM)
  • Study the E1 frame structure and timing specifications
  • Understand the difference between TS0 (synchronization) and TS16 (signaling)
  • Familiarize yourself with HDB3 line coding principles
  • Calculate the expected bit rate: 32 × 8 × 8000 = 2.048 Mbps

2Equipment Setup

  • Launch the E1 Virtual Laboratory simulation
  • Set the simulation speed to moderate (5/10) for initial observation
  • Select "Random" data pattern for realistic behavior
  • Start with 4 active channels for clarity, then increase to 30
  • Verify the control panel displays are functioning

3Multiplexer Operation Study

  1. Observe Input Channels: Note the individual bit streams in each channel box
  2. Start Simulation: Click "Start" and observe the multiplexer waveform
  3. Frame Assembly: Watch how bits from different channels are interleaved
  4. Sync Pattern: Identify the TS0 frame alignment word (alternating pattern)
  5. Measure Timing: Verify that each time slot occupies 3.9 μs (125 μs/32)
  6. Data Rate Verification: Confirm the output shows 2.048 Mbps

4Demultiplexer Operation Study

  1. Frame Detection: Observe how the demultiplexer identifies TS0
  2. Channel Extraction: Watch individual channels being separated
  3. Sync Recovery: Note the "Sync Status" indicator
  4. Output Verification: Compare output with original input data
  5. Signaling: If implemented, observe TS16 processing

5Parameter Variation Experiments

Parameter Variation Expected Observation
Active Channels 1 → 30 Frame utilization increases, bit rate constant
Simulation Speed 1 → 10 Animation speed changes, timing relationships preserved
Data Pattern Random/Increment/Alternate Different spectral characteristics in waveform

6Measurements and Data Collection

Record the following in your lab notebook:

  • Frame duration: ______ μs
  • Time slot duration: ______ μs
  • Bit duration: ______ μs
  • Number of frames per second: ______
  • Total bits per frame: ______
  • Channel data rate: ______ kbps
  • Total E1 rate: ______ Mbps

7Post-Lab Analysis

  • Calculate the efficiency: (30/32) × 100 = 93.75%
  • Determine overhead percentage: (2/32) × 100 = 6.25%
  • Compare E1 with T1 systems (1.544 Mbps, 24 channels)
  • Analyze the importance of frame synchronization
  • Discuss applications of E1 in modern telecommunications

📋 Guidelines for Lab Report Writing

1. Title Page

  • Experiment Title: E1 Multiplexer and Demultiplexer System
  • Course Name and Code
  • Student Name and ID
  • Date of Experiment
  • Instructor Name

2. Abstract/Objective (5%)

Write a brief summary (100-150 words) covering:

  • Purpose of the experiment
  • Key concepts investigated (TDM, E1 framing)
  • Main findings or observations
  • Conclusion about E1 system operation

3. Theory (20%)

Include comprehensive discussion of:

  • Principles of Time Division Multiplexing
  • E1 frame structure with diagram
  • Time slot allocation and purposes
  • PCM encoding (A-law/μ-law)
  • Frame and multiframe synchronization
  • HDB3 line coding (brief overview)
  • Mathematical derivations for bit rate calculations

4. Equipment and Software (5%)

  • E1 Virtual Laboratory Software (HTML5-based)
  • Computer system specifications
  • Browser used for simulation
  • Any additional tools for analysis

5. Procedure (15%)

Document the step-by-step procedure followed:

  • Initial setup and configuration
  • Parameters selected (channels, speed, pattern)
  • Measurements taken at each stage
  • Any modifications or additional tests performed

6. Results and Observations (25%)

Present your findings with:

  • Waveform screenshots from simulation
  • Frame structure diagrams (hand-drawn or captured)
  • Data tables showing:
    • Channel inputs vs outputs
    • Timing measurements
    • Frame count statistics
  • Observations about synchronization
  • Analysis of different data patterns

7. Calculations (10%)

Show detailed calculations for:

1. Frame Duration = 125 μs
2. Frame Rate = 1/125μs = 8000 frames/sec
3. Bits per Frame = 32 × 8 = 256 bits
4. Bit Rate = 256 × 8000 = 2.048 Mbps
5. Channel Rate = 8 × 8000 = 64 kbps
6. Efficiency = (30/32) × 100 = 93.75%

8. Discussion and Analysis (15%)

Provide critical analysis:

  • Comparison of theoretical vs observed values
  • Sources of error or discrepancy
  • Importance of TS0 in maintaining synchronization
  • Role of TS16 in signaling
  • Advantages of E1 over analog systems
  • Comparison with T1 (North American standard)
  • Modern applications of E1 (PDH, SDH networks)

9. Conclusion (5%)

Summarize key learnings:

  • Understanding of TDM principles demonstrated
  • E1 frame structure comprehension
  • Ability to calculate digital transmission parameters
  • Practical insights into multiplexing operations

10. References

List all textbooks, websites, and resources consulted. Use IEEE or APA format.

Grading Rubric:

Section Weight Criteria
Abstract 5% Clarity, completeness
Theory 20% Accuracy, depth, diagrams
Procedure 15% Clarity, reproducibility
Results 25% Presentation, accuracy
Calculations 10% Correctness, showing work
Discussion 15% Critical thinking, analysis
Conclusion 5% Summary, insights
Presentation 5% Format, grammar, neatness